[pamarin]

I own a 2011 X3 2.0D fitted with Pirelli P7 Cinturato 225/60R17 99V Run Flat Tyres which I understand are considered 'summer tyres'.

Now normally this is no problem for me as I live in Brisbane, which is in the sub-tropics, and the lowest ever recorded temperature is +3oC (+37oF).

However I'm taking our X3 from on a holiday trip from Brisbane to Canberra for a week in the near future where the current temperature range is from overnight lows of -3oC (+27oF) and daytime highs of +15oC (+59oF). I have a short 2 day side trip planned up to the Australian Alpine region where current temperature range is from overnight lows of -5oC (+23oF) and daytime highs of +6oC (+43oF).

I'm getting conflicting advice about the suitability of the P7 summer tyres. My BMW owners hand book say that they are not recommended for operation on 'winter roads or temperatures below +7oC (+45oF)'. I can't find any specifics on the Pirelli site about operating temperature ranges but I've read some US and Canada blog sites saying that at below +4oC (+40oF) grip starts to drop off, while a UK site suggested that at +3oC (+37oF) winter tyre performance seemed superior to an equivalent summer tyre. Other sites suggest that it is not until you get to -14oC (+7oF) that you lose all grip capacity as the summer tyres have by this point gone rock hard.

The official snow season is still 4 weeks away so there may not even be any snow on the roads yet.

I'll be talking to my local BMW dealer this week but I'm keen to hear any comments from Bimmerfesters that might help me decide if one week at sometimes near zero temperatures means I should get winter tyres.

If anyone can direct me to any sites that have specific information on realistic operating temperature ranges for the P7 that would be appreciated.

Also as a post script does anyone know if the standard engine coolant and wiper fluid is already sufficient for sub zero temperature operations.